Method and apparatus for fingerprint motion tracking using an in-line array for use in navigation applications

ABSTRACT

The invention provides an independent relative motion sensor for use in navigation operations using a fingerprint that do not require the power demanded by conventional devices. The independent relative motion sensor includes a linear array of sensing elements that captures a narrow string of data that is indicative of fingerprint features along a relatively narrow sample. This string of data is used to determine the velocity of travel for use in navigation operations. Using multiple sensors, motion and direction data can be computed and used to provide two-dimensional direction for navigating an object, such as a cursor on a monitor. The invention can be incorporated in an electronic device to provide improved navigation operations that demand less power.

BACKGROUND

The invention relates generally to technology for sensing and recordingfingerprints and, more particularly to systems, devices and methods forfingerprint motion tracking alone and in combination with fingerprintimage processing and navigation operations.

A number of devices and techniques exist for sensing, capturing, andreconstructing the image of a fingerprint as it moves across a sensorarray. Though many devices exist to sense and record an entirefingerprint, partial fingerprint sensing devices have been developed forsmall portable devices to save space. The sensing devices themselvesvary widely, and many devices and related techniques exist forsensitively detecting the presence of the finger surface and featureslocated on the surface that make up the unique fingerprint of a person.For example, one common configuration used for a fingerprint sensingsurface includes CCD (charge coupled devices) or C-MOS circuits. Thesecomponents are embedded in a sensing surface to form a matrix ofpiezoelectric elements that generate signals in response to pressureapplied to the surface by a finger. These signals are read by aprocessor and used to reconstruct the fingerprint of a user and toverify identification. Other devices include a matrix of optical sensorsthat read light reflected off of a person's finger and onto opticalelements The reflected light is converted to a signal that defines thefingerprint of the finger analyzed and is used to reconstruct thefingerprint and to verify identification. More modern devices includestatic or radio frequency (RF) devices configured to measure theintensity of electric fields conducted by finger ridges and valleys tosense and capture the fingerprint image. Regardless of the method usedto sense the fingerprint, conventional devices and techniques havecommon drawbacks, particularly when used in combination with portableelectronic devices. These devices require small component size becauseof a lack of space and surface area due to the devices small size, andfurther require that any power demand be as small as possible due tolimited battery life.

Specifically, devices exist that have a sensing area that is smallerthan the fingerprint area to be imaged. Such devices are greatly desiredbecause they take up much less space than a full fingerprint sensor.This is a very useful feature for small portable devices. These sensingdevices generally consist of one or more imaging lines disposedperpendicular to the axis of motion. As the finger surface is movedacross the sensor, portions of the fingerprint are sensed and capturedby the device. These portions are subsequently reconstructed in a mosaicor overlapping manner. In operation however, current conventionaldevices have severe drawbacks. They generally require extensiveprocessing resources for computing the algorithms and required data forreconstructing fingerprints.

For applications of fingerprint identification devices in portableelectronics, such as laptops and cellular telephones, low powerconsumption is a strict requirement. Therefore, it is important tomaintain minimal computation processing in such applications. Again,present conventional fingerprint sensor technology requires asubstantial amount of processing, and thus requires a large amount ofpower to perform the required tasks for reconstructing fingerprints foridentification. One major problem is that a large amount of pixelinformation is required to be recorded and matched in a short a mount oftime, burdening the device processor and consuming substantial power.This is a big problem with small devices, which already haverestrictions on power consumption.

One conventional device is described in U.S. Pat. No. 6,002,815 ofImmega, et al. The technique used by the Immega device is based on theamount of time required for the finger to travel a fixed distancebetween two parallel image lines that are oriented perpendicular to theaxis of motion. After a time history of samples are captured, the speedis determined by finding the time delay that provides the best matchbetween data from the first line and data to from the second line. Thedevice captures the entire image of an object and stores the image lineby line. Such an object is illustrated as a photo copy of a document,and the reference does not suggest a fingerprint or other image. Thus,it is directed to a device and method for scanning an image passing overa perpendicular slit pair at a variable speed, as opposed to objectsthat pass over the slit pair at a fixed speed. It does not address theproblem of excessive processor power expended to perform the process.Also, the perpendicular lines of the image are used for determining thespeed of the object as it passes through the perpendicular slit wherethe image is captured. These recorded lines are also used inreconstructing the image when the scan is complete. Thus, a large amountof data is processed and stored in the process. The amount of processingresources required to calculate the speed at any given moment isimmense, where the resources include time required, calculation by theprocessor and power demanded by the processor. Furthermore, this timeseries approach has the disadvantage that it is not possible to quicklydetermine an absolute distance of motion by comparing only theinstantaneous data from the two image lines. This is true for all casesother than for the rare coincidental case where the finger happens totravel exactly the distance between the image lines during the intervalbetween the two samples. Another problem arises when the object ismoving much slower than the sample rate of the device. In this case, thenumber of samples needed to find a match is substantial. In addition, atslow speeds, the device must compare a larger number of stored lines inorder to find a match. This greatly increases the computationalrequirements, placing a substantial burden on the device processor.Thus, expensive high order processors are required for adequateperformance and substantial power is needed to operate such processors.

Another technique is described in U.S. Pat. No. 6,289,114 of Mainguet. Adevice utilizing this method reconstructs fingerprints based on sensingand recording images taken of rectangular slices of the fingerprint andpiecing them together using an overlapping mosaic algorithm. LikeImmega, the technique described in Mainguet is also computationallyburdensome on the device processor. Furthermore, the Mainguet methodrequires a substantial amount of memory as well as a larger number ofimaging pixels in order to properly record the images. Again, thismethod demands substantial power to perform algorithms, a big problemfor power rationed portable devices.

For accurate fingerprint capture, it is often advantageous to provide anavigation function with the same device used for fingerprint sensing.The navigation function can provide more functionality in as little areaas possible in a portable device, and provide a more accuratefingerprint image. However, conventional devices and methods fornavigation require substantial processor resources, and thus demand morepower. In such devices, in order to sense finger motion, the sensingdevice must sample the image at a periodic rate that is fast enough toensure that a moving feature will be sampled when it passes both theprimary imaging line and the auxiliary line of pixels. As a consequence,the sensor needs to operate at full imaging speeds, thus consuming fullimaging power while in the navigation mode. Consequently, conventionalnavigation methods demand substantial power, and are thus impracticalfor small devices.

Thus, there exists a great need in the art for a more efficient means toaccurately sense and capture fingerprints on portable devices and alsoto provide navigation operations without unduly demanding power. As willbe seen, the invention provides a means to overcome the shortcomings ofconventional systems in an elegant manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagrammatic view of a sensor configured according to theinvention;

Figure B is a diagrammatic view of a sensor configured according to theinvention;

FIG. 2A is a diagrammatic view of a sensor configured according to theinvention;

FIG. 2B is a diagrammatic view of a sensor configured according to theinvention;

FIG. 2C is a diagrammatic view of a fingerprint scan result;

FIG. 2D is a diagrammatic view of a fingerprint scan result;

FIG. 2E is a diagrammatic view of a sensor configured according to theinvention;

FIG. 2F is a diagrammatic view of a sensor configured according to theinvention;

FIG. 2G is a diagrammatic view of a sensor configured according to theinvention;

FIG. 3 is a diagrammatic view of a sensor configured according to theinvention;

FIG. 4 is a diagrammatic view of a sensor configured according to theinvention;

FIG. 5A is a diagrammatic view of a sensor configured according to theinvention;

FIG. 5B is a diagrammatic view of a sensor configured according to theinvention;

FIG. 6 is a diagrammatic view of a sensor configured according to theinvention;

FIG. 7 is a diagrammatic view of a sensor configured according to theinvention;

FIG. 8A is a diagrammatic view of a sensor configured according to theinvention;

FIG. 8B is a diagrammatic view of a sensor configured according to theinvention;

FIG. 8C is a diagrammatic view of a sensor configured according to theinvention;

FIG. 9A is a diagrammatic view of a system configured according to theinvention;

FIG. 9B is a diagrammatic view of a system configured according to theinvention;

FIGS. 10 a-b is are diagrammatic views of a sensor and fingerprintconfigured according to the invention;

FIGS. 11 a-j are diagrammatic views of a sensor and fingerprintconfigured according to the invention.

FIG. 12 is a diagrammatic view of a sensor and fingerprint configuredaccording to the invention.

FIG. 12B is a flow diagram of method configured according to theinvention;

FIG. 13 is a flow diagram of method configured according to theinvention;

FIG. 14 is a flow diagram of method configured according to theinvention;

FIG. 15 is a flow diagram of method configured according to theinvention; and

FIG. 16 is a flow diagram of method configured according to theinvention.

DETAILED DESCRIPTION

The invention provides an independent relative motion sensor for use innavigation operations using a fingerprint that do not require the powerdemanded by conventional devices. The independent relative motion sensorincludes a linear array of sensing elements that captures a narrowstring of data that is indicative of fingerprint features along arelatively narrow sample. This string of data is used to determine thevelocity of travel for use in navigation operations. Using multiplesensors, motion and direction data can be computed and used to providetwo-dimensional direction for navigating an object, such as a cursor ona monitor. The invention can be incorporated in an electronic device toprovide improved navigation operations that demand less power.

In operation, the linear sensor array senses and captures fingerprintfeatures in the form of a string of data signals by first sensing thefeatures in an initial sensing and capture, and this is followed by oneor more subsequent operations where a sample is taken of a subset of thefingerprint features are captured again over a known time period. Thistime period may be predetermined or measured as time progresses betweensensing and capturing of the samples. Once at least two samples aretaken, a subsequent sample is compared against a previous sample todetermine the amount shift of the previous sample relative to thesubsequent sample. In one embodiment, a single linear line of sensorpixels is used to sense a one-dimensional track of fingerprint features,and the signal sensed by the pixels is converted from an analog signalto a digital signal, where the features are then represented as a stringof digital values. For example, the ridges of the fingerprint featuresmay be represented as logical ones, and valleys represented as logicalzeros.

When compared, the first string of digital values from one sample can becompared to the second string in a one to one relationship, and asimilarity score can be produced that measures the number of matchingvalues. If there is an immediate match, where both strings aresubstantially identical, then this would indicate that there was nomovement during the time between which the two samples were taken. Ifthere is not an immediate match, then this would indicate that there wassome movement, and additional comparisons may be needed to determine thedistance traveled. For each comparison, the strings of digital valuescan be shifted one or more pixels at a time. Once a good match is found,the distance traveled by the fingerprint is simply the number of pixelsshifted times the distance between the pixels, which may be measuredfrom the center point of one pixel to the center point of another pixelin the array of pixel sensors for example.

In one embodiment, a predetermined number of comparisons can be madealong with corresponding similarity scores. The process may then choosethe highest score to determine the most accurate comparison. The numberof pixels that were shifted to get the best comparison can then be usedto determine the distance traveled, since the size of and distancebetween the pixels can be predetermined, and the number of pixels canthus be used to measure the distance traveled by the fingerprint acrossthe motion sensor over the time period of the motion.

In another embodiment, the process could make comparisons and generatescores to measure against a predetermined threshold, rather than makinga predetermined number of comparisons. In this embodiment, thesimilarity score from each comparison can be measured after thecomparison is made. If the score is within the threshold, then it can beused to indicate the amount of shift from one sample to another. Thiscan then be used to determine the distance traveled by the fingerprintacross the linear motion sensor.

In one embodiment, generally, the invention provides a fingerprintmotion tracking system and method, where a single linear sensor array isconfigured to sense features of a fingerprint along an axis of fingermotion. The linear sensor array includes a plurality of substantiallycontiguous sensing elements or pixels configured to capture a segment ofimage data that represents a series of fingerprint features passing overa sensor surface. A buffer is configured to receive and store image datafrom the linear sensor array. And, a processing element is configured togenerate fingerprint motion data. The linear sensor array may beconfigured to repeatedly sense at least two substantially contiguoussegments of fingerprint data, and the processor can generate motion databased on at least two sensed contiguous segments of fingerprint data. Inoperation, the linear sensor array is configured to sense a first set offeatures of a fingerprint along an axis of finger motion and to generatea first set of image data captured by a plurality of substantiallycontiguous pixels of the sensor array. The linear sensor array is alsoconfigured to subsequently sense a second set of features of thefingerprint along an axis of finger motion and to generate a second setof image data captured by a plurality of substantially contiguous pixelsof the sensor array. The processing element can then compare first andsecond sets of image data to determine the distance traveled by thefingerprint over a time interval.

As used herein, linear sensor array is a generic term that relates to aportion of sensing elements, whether they are pixels in an opticalreader, a static or radio frequency reader that reads electric fieldintensity to capture a fingerprint image, piezoelectric components intouch-sensitive circuit fingerprint readers, or other elementsindicative of fingerprint readers, where the elements are used to sensea portion of the fingerprint, rather than the entire fingerprint. Suchsensor arrays may be configured in a number of ways within a matrix ofwell known sensor devices. For example, several modern configurationsare described and illustrated in pending U.S. patent application Ser.No. 11/243,100 entitled: Fingerprint Sensing Assemblies and Methods ofMaking; U.S. patent application Ser. No. 11/112,338 entitled: Methodsand Apparatus for Acquiring a Swiped Fingerprint Image; U.S. patentapplication Ser. No. 11/107,682, entitled: Fingerprint Sensing Methodsand Apparatus; U.S. patent application Ser. No. 10/005,643 entitled:Swiped aperture capacitive fingerprint sensing systems and methods, andother applications that are all assigned to common assignee Validity,Inc. Also, many other types of sensor matrices exist in the art directedto capturing fingerprint images. The invention is directed to a novelsystem, device and method that is not limited in application to anyparticular sensor matrix or array configuration. In fact, the inventioncan be used in conjunction with or incorporated into such configurationsto improve performance, and further to reduce the processing resourcesrequired to capture and reconstruct images.

According to the invention, the linear sensor is substantiallycontiguous, which is to say that the sensor elements are in a relativeproximity to each other so that a first reading of a portion offingerprint features can be taken, followed by a second reading after ashort period of time from another position. The two samples can becompared to determine the relative distance traveled by the fingerprintsurface in relation to the sensor surface. The linear sensor isconfigured to merely take a relatively small sample of the fingerprintat one point in time, then another at a subsequent time. These twosamples are used to determine movement of the fingerprint. Two or moresamples maybe compared in order to compute direction and velocity of afingerprint surface relative to the linear sensing elements. Thesesamples may be linear, as described below and illustrated in thedrawings, so that a linear array of fingerprint features can be recordedand easily compared to provide a basis for motion, distance traveledover time. If more than one sensor is employed, it is possible todetermine direction of motion using vector addition with the differentlinear samples taken. Thus, some of the functions provided by theinvention are a result of taking a linear sample to give a basis forvector analysis. However, those skilled in the art will understand that,given the description below and the related drawings, other embodimentsare possible using other configurations of motion sensors, which wouldnot depart from the spirit and scope of the invention, which is definedby the appended claims and their equivalents, as well as any claims andamendments presented in the future and their equivalents.

One useful feature of the invention is that ambiguity in results issubstantially prevented. If properly configured, a system configuredaccording to the invention can consistently produce a result, where atleast two samples can be taken such that the features of one sampleoverlap with another sample. Then, comparisons can be made to determinethe amount of shift, indicating the amount of movement of thefingerprint across the linear sensor. In prior art systems and methods,it is often the case that no result occurs, and a singularity results.Thus, a user would need to repeat sensing the fingerprint. In somesystems, substantial predictor algorithms have been created in anattempt to compensate or resolve the singularity when it occurs. Suchapplications are very large and demand a good deal of computation andprocessing resources, which would greatly bog down a portable device.According to the invention, sensing motion of a fingerprint issubstantially certain, where samples taken from the fingerprint surfaceare consistently reliable. This is particularly important in navigationapplications, where relative movement of the finger translates tomovement of an object such as a cursor on a graphical user interface(GUI), discussed further below.

In one embodiment, the linear sensor array may be used alone todetermine linear movement of a fingerprint. In another embodiment, thesingle sensor array may be used in conjunction with one or more otherlinear sensor arrays to determine movement in two dimensions. In eitherembodiment, the linear sensor arrays are utilized solely for determiningmotion. If the motion of the analyzed fingerprint occurs generally alonga predetermined axis of motion, the single linear sensor array can beutilized to sense the velocity of the fingerprint being analyzed. Tocapture and record the motion of a fingerprint that is not directedalong a predetermined axis of motion, two or more linear arrays (aplurality of arrays) can be used together to sense and record suchmotion, and a processor can determine the direction and speed of thefingerprint using vector arithmetic.

In yet another embodiment, one or more such linear arrays may be used inconjunction with a fingerprint sensor matrix to more accurately captureand reconstruct a fingerprint image. The sensor matrix can be configuredto sense and capture an image of a portion of a fingerprint beinganalyzed, and the one or more linear arrays can provide motioninformation for use in reconstructing a fingerprint image. A device soconfigured would be able to more accurately sense, capture, record andreconstruct a fingerprint image using less processing resources thanconventional devices and methods.

The primary distinction between the invention and the prior art, Immegaand Mainguet for example, is that the invention separates the analysisof motion from the capturing of the entire fingerprint image. Theconcept described in Immega, for example, requires the entire image tobe captured and recoded line by line. The lines are used to bothdetermine speed of the object being sensed and recorded and alsocalculate the speed of the object as it is passed over the perpendicularslot. Immega requires immense processing and storage resources to sense,capture, record and reconstruct the image, and all of these functionsare carried out by processing the entire lot of image data captured andrecorded. Similarly, a device configured according to Mainguet mustcapture large portions of the fingerprint image and requires substantialprocessing and storage resources to overlap and match the image mosaicsto reconstruct the image. In stark contrast, the invention provides ameans for detecting motion of a fingerprint separately from the processof capturing a fingerprint image, and uses the motion information tomore efficiently reconstruct the fingerprint image using less processingand storage resources. The invention further provides a means forgenerating navigation information using the same mechanism.

Alternatively, in yet another embodiment, one or more arrays can be usedto generate motion information for use in accurate navigationaloperations, such as for use in navigating a cursor on a graphical userinterface (GUI). Utilizing the improved processing functions of theinvention, an improved navigation device can be constructed that iscompatible with a portable device that has the power and processingrestrictions discussed above. Examples of such embodiments are describedand illustrated below.

A motion sensor configured according to the invention uses substantiallyless space and power compared to conventional configurations for motionsensing, navigation and fingerprint image reconstruction. Such aconfiguration can further provide aid to conventional fingerprintreconstructing processes by better sensing motion of a finger while itis being analyzed by a sensing device. This allows a fingerprint sensingdevice the ability to reconstruct a fingerprint analyzed by afingerprint sensor with reduced power. Utilizing the invention,conventional processes that need to match and construct fragmentedimages of a fingerprint, particularly devices that sense and process afingerprint in portions, can be optimized with information related tofingerprint motion that occurs while a fingerprint surface is beingread. Also, using this unique motion detection technology, optimalnavigation functions can be provided that demand significantly lesspower than conventional devices. Such navigation functions can enable alow power navigation device to be integrated in a portable devicesystem, such as a mouse pad used to move a cursor across a graphicaluser interface (GUII) on portable electronic devices including cellularphones, laptop computers, personal data assistants (PDAs), and otherdevices where low power navigation functions are desired. A novel systemand method are provided that uses minimal space and processing resourcesin providing accurate motion detection from which fingerprint sensors aswell as navigation systems can greatly benefit.

A device or system configured according to the invention can beimplemented as a stand alone navigation device, or a device to provideimage reconstruction information for use with a line imaging device thatmatches and assembles a fingerprint image. Such a line imaging devicemay be any imaging device configured to sense and capture portions of afingerprint, whether it captures individual perpendicular image lines ofa fingerprint, or multiple perpendicular lines. In operation, a motiondetection device can operate as a separate motion detection and/ordirection detection device. Alternatively, a motion detection device canbe used in conjunction with a line imaging device to more accurately andefficiently sense, capture, store and reconstruct a fingerprint image. Adevice configured according to the invention may include a single arrayof finger ridge sensing pixels or data sensor points centrally locatedalong the principal axis of motion to be detected, a sampling system toperiodically sample the finger contact across the array, and acomputational module or element that compares two sets of samplescollected at different times to determine the distance traveled whilebetween the two sample times. According to the invention, the motionsensor pixels do not necessarily need to have the same resolution as theline imager. The motion sensor pixels may in fact use a differentsensing technique than the imager.

Again, the invention provides separate operations for detecting motionand for sensing and capturing a fingerprint image. Thus, the techniquesused for the separate processes can be the same or may be differentdepending on the application. Those skilled in the art will understandthat different variations of the separate processes are possible usingknown techniques and techniques can be derived without any undueexperimentation. Such variations would not depart from the spirit andscope of the invention.

In another embodiment, the invention provides the capability ofmulti-axis motion sensing with additional off-axis sensing arrays. Inthis embodiment, there are two or more (a plurality of) sensor arraysfor detecting motion, and each axis is independently measured todetermine the component of velocity in that axis. The velocitycomponents from the individual axes are used to compute a vector sum todetermine the actual direction and velocity of motion of the finger withrespect to the sensor surface. According to the invention, it is notnecessary to capture the full image of the fingerprint in order todetermine the distance traveled and the velocity. It is only necessaryto capture a linear sample of fingerprint features along the line ofmotion of the fingerprint. In one embodiment, a plurality of samples,such as two or three samples, are captured by motion sensor pixels andare used to determine the distance traveled across the axis of motion ofthe fingerprint relative to the sensor surface and the velocity at whichthe motion occurs. This information can also be used in navigationaloperations, and can further be used in combination with a fingerprintimager to aid in reconstructing a fingerprint image. Utilizing theinvention, either application can be configured in an economical anduseful manner. Moreover, the operation of such a sensor or navigationaldevice can be optimized to consume substantially less power thanconventional devices, which require excessive processor operations forreassembly of the fingerprint image. And, given the motion informationgenerated by a system configured according to the invention, thedistance traveled and velocity of the fingerprint can be used to moreaccurately and efficiently reconstruct a full fingerprint or to betterrepresent relative motion information for use in navigation.

Aligning the pixels along the axis of motion, rather than perpendicularto it, enables the use of motion detection algorithms that can be bothtime-variant and distance variant. This enables development ofalgorithms that utilize short distance measurement over long timeperiods for low speed motion and longer distance motion to moreaccurately measure higher speed motion, thus optimizing response timeand accuracy. Both embodiments share the advantages gained by acquiringand comparing multiple spatial measurements of the fingerprint patternat each sampling instance. Because multiple samples are taken andcompared simultaneously, effects of sampling error, both due to noiseand imprecision in the sampling of the finger pattern, are minimized.Also, because samples are taken at multiple locations along the axis ofmotion simultaneously at each sampling period, the images from twosampling periods can be compared to detect if there had been anysignificant finger motion between the two sample times. One sharedadvantage is that both systems are capable of detecting under-samplingof the image being acquired by the line imager, as a consequence oftheir ability to detect motion of multiple pixels in a short timeinterval.

An embodiment using a single segmented motion sensor array offers theadvantage of detecting motion over a shorter range of distance. Thisprovides faster response time, particularly at low finger speeds thatmay be encountered in navigation applications. Because this embodimentis sensitive to single pixel motion, it provides unique features thatmay also reduce the memory requirements for the computational elements.In order to provide a navigation device, as well as to detect andcorrect for finger motion that is not completely aligned with thedesired axis, either of the embodiments may be combined in ensemblessuch that one sensor is aligned on the axis of motion, and additionalsensors aligned at an angle (such as 22.5 or 30 degrees) to theprincipal axis of finger motion. Examples of different embodiments arediscussed below.

Referring to FIG. 1A, a diagrammatic view of motion detection andtracking system configured according to the invention is illustrated. Anintegrated circuit package 100 is illustrated having circuits andpossibly software embedded (not shown) and electrical connections 101for integration in and connection with a system that utilizes thecircuit package. FIG. 1 illustrates an embodiment of the invention wherea finger 104 can move its fingerprint surface 106 against sensor surface108 to be read by the sensors 110, 112. These sensors can pick upmovement information of a fingerprint for use in navigationalapplications, or can be used in conjunction with an integratedfingerprint sensor surface 108 to simultaneously capture and recordportions of a fingerprint. Such a system configured according to theinvention may be a stand alone component as shown, or can be integratedwith other circuits for more space and power savings as well asefficiency. Those skilled in the art will understand that manyvariations of the configuration are possible, and that the invention isnot limited to any particular configuration, but is defined by theclaims and all equivalents.

The system further includes a sensor module 102 that is used to sense auser's finger 104 fingerprint surface 106 when it is moved acrossfingerprint sensing surface 108. As can be seen, the fingerprint sensingsurface 108 is illustrated as a narrow surface that is designed to senseand capture portions of a fingerprint as it is moves across the sensor.These portions can be subsequently reconstructed according to theinvention using motion information from the motion sensors 110,112.Thus, the sensor components illustrated in FIG. 1 have multipleutilities, and can be configured in devices that utilize part or all ofsuch utilities, whether it is a stand alone motion sensor configured tosense movement and velocity in one direction, a multidirectional motionsensor configured to sense movement and velocity in several directions,or a combination device configured to sense motion either in one or more(one or more meaning a plurality of directions) directions and used incombination with a fingerprint sensor surface that reads portions offingerprints and reassembles the fingerprints using the motioninformation from motion sensors. The features and benefits of severalembodiments of the invention are discussed and illustrated below. Again,these are intended as mere examples of different embodiments, and arenot intended as an exhaustive set of samples. And again, those skilledin the art will understand that these and other embodiments of theinvention described herein are illustrative of the invention and are notintended to limit the spirit and scope of the invention, which isdefined by the appended claims and all equivalents, including claimsappended herein upon filing and also those as possibly amended at alater date.

Referring to FIG. 1B, a side view of the sensor system of FIG. 1A isillustrated. In operation, the finger 104 is placed by a user onto thesensor surface 107, which includes fingerprint sensing surface 108, sothat the fingerprint sensing surface 108 and the sensor surface 106 arejuxtaposed relative to each other. The finger 104 and sensor 100 movesin opposite directions A, B, so that the sensor 102 can move across andanalyze the fingerprint surface 106. In different applications anddevices, this interaction may take on many forms. A user may hold thefingerprint surface stationary so that sensor 102 can move relative tothe fingerprint, similar to the operations of a photocopy machine. Or,if the sensor is fixed in a surface, such as on the surface of a laptopcomputer or cellular phone, the user can move the fingerprint surface106 by rubbing it against and along the fingerprint sensing surface 108so that the sensor 102 can analyze and read the fingerprint.

Referring to FIG. 2A, one practical application of a navigational systemis illustrated, where a portable device 202, such as a portable musicplayer, a cellular phone, PDA or other device, has a graphical userinterface (GUI) or screen 204, a cursor 206 that may appear on thescreen that is capable of being moved across the screen under control ofa user navigating a touch-sensitive cursor 208. The touch sensitivecursor has navigational indicia 210, which may be merely directionalindicators located about sensor 102 that is located within or about thattouch-sensitive cursor that acts as a navigational pad, similar to thatof a mouse pad commonly used on laptop computers. According to theinvention, such a navigational pad can be greatly enhanced using sensortechnology according to the invention, where directional movementsensors 110,112 are used to guide the cursor 206 for searching for andselecting indicia such as toolbar items or icons for opening files,photos and other items when selected. In some applications, a multi-stepsensor can read the fingerprint structures for guidance at one level,and may select an indicia by pressing harder on the sensor for anotherlevel of sensing. Thus, a user can move the cursor around by lightlypressing on and moving a finger along the surface, then pressing harderwhen selecting an icon, toolbar or other indicia. Utilizing theinvention, a more efficient navigation tool can be adapted to performall of these tasks at low power and high accuracy, a very adaptablefeature for portable devices.

Referring to FIG. 2B, another embodiment of the invention isillustrated, where the integrated circuit (IC) chip 114 is separate fromthe sensor surface 108(b). In the illustration of FIGS. 1A and 1B, thesensor surface may be located on top of an IC as in many conventionalconfigurations, but with the novel array sensors 110,112 of theinvention. FIG. 2B illustrates a novel configuration where the sensorsurface 108(b) is located on a film 118, ad the IC 116 is locatedseparately, allowing for more flexible and useful applications. Asdiscussed herein, the invention can be applied either type ofconfiguration, and is adaptable to any application where motion anddirection information may be useful, such as for navigating objects suchas cursors on a graphical user interface, or other applications.

Referring again to FIG. 1A, the surface 108 has embedded motion sensors112 that, according to the invention, operate to detect the presence andmotion of a fingerprint surface 106 about the sensor surface 108. Asingle motion sensor 110, aligned with a general fingerprint motiondirection for detecting distance traveled by the fingerprint across thesensor over a period of time. This allows a processor to compute thevelocity of the fingerprint over the sensor surface. In anotherembodiment, there may be a single motion sensor 110 on the surface 108,or there may be a plurality, two or more motion sensors 110,112, on thesurface 108, depending on the application. The additional sensors 112may be used to detect direction of a fingerprint's motion across thesensor surface. In practical applications, a user may not move thefinger exactly parallel with the sensor 110. A user may rub thefingerprint surface 106 at an angle with respect to the axis of thesensor 110. A processor analyzing the velocity of the fingerprint motionmay then end up with an inaccurate velocity reading. This may beimportant when the data generated by the sensor is used forreconstructing a fingerprint, or when the sensor data is used fornavigational purposes. According to this additional embodiment of theinvention, the additional sensors 112 can be used to determine thedirection of the fingerprint surface when it is being analyzed. Usingthe data captured by the sensors, a processor can apply vector analysisto generate motion information. This motion information can be used inprocesses for reconstructing the fingerprint images, or for navigationprocesses.

Referring to FIG. 2E, another application of a navigation sensor isillustrated as an alternative for providing navigational information tocontrol a cursor 216 shown on computer monitor 212 of a conventionaldesktop computer system, where the navigational sensor 218 is providedas an alternative to a conventional mouse used for a computer. Such amouse may be part of a keyboard as shown, or may be implemented as aseparate device apart from the keyboard. The sensor 218 includes asensor surface 208 that may have directional indicators 210 for a user,and array sensors 110,112. The IC 219 may be separate from the sensorsurface 208 as described above along with other similar figures showingvarious embodiments.

Referring to FIG. 2F, yet another embodiment of a navigational sensor220 is illustrated, which can also be implemented as an alternative to aconventional computer mouse. The sensor 220 may include individualsensors 222,224,226 for individual activation by a user. Theseindividual sensors may be simple pressure activated buttons, RF sensors,or other sensors for selecting or otherwise manipulating or activatingobjects chosen on a monitor with a cursor. Such individual sensors maybe integrated on the device 220, such as on a common film, or may beseparate yet accessible by a user's touch. Sensor pad 228 includes arraysensors configured to sense motion of a fingerprint surface relative tothe pad. IC 230 may be configured on the same film, or may be entirelyseparate. The sensor 220 may be implemented on a keyboard such as sensor218 of FIG. 2E, or may be implemented on a laptop computer, cellularphone, personal data assistant, automotive dashboard, or other devicethat could utilize the operations of the navigational sensor.

Referring to FIG. 2G, yet another embodiment of a navigational sensor232 is illustrated. Sensor 232 is configured as a small fingerprintnavigation sensor having sensors 234,236,238, a narrow slit sensorsurface 240 and sensor 242. Each of the sensors can be configured tosense motion, pressure or other stimuli performed by a user innavigating operations. Those skilled in the art will understand thatmany variations of sensors, buttons and other accessories can beimplemented according to the invention to allow a user to operatedifferent devices, systems and operations with navigation information.

FIGS. 3-7 discussed below have a similar numbering pattern, where thesensor surface 107 includes the two other sensing surfaces: fingerprintsensing surface 108 and motion sensors 110 and 112. The different motionsensing devices, whether included with an image sensor for sensing afinger print image for future reconstruction, can be utilized fornavigational operations. These different embodiments are described belowin relation to sensing, capturing and reconstructing fingerprint images,but are also applicable in providing motion and direction informationfor use as navigational information, such as for use in navigating acursor relative to the motion of a fingerprint over motion sensors. Thedifferent embodiments, though similar in general function, areseparately described to differentiate the different components in thedifferent embodiments. These are intended as mere examples of differentembodiments, and are not intended as an exhaustive set of samples.Again, those skilled in the art will understand that these and otherembodiments of the invention described herein are illustrative of theinvention and do not limit the spirit and scope of the invention, whichis defined by the appended claims and all equivalents, including claimsappended herein upon filing and also those as possibly amended at alater date.

According to another embodiment 102(a) of the invention illustrated inFIG. 3, the sensor surface 108(a) may include image sensing elementsused for broadly sensing and recording the fingerprint features. Inaddition, a motion sensor 110(a) is included for sensing and recordingthe motion of the fingerprint. Such a device may be a single sensorembedded within the two dimensions of the sensor surface 107(a), withthe fingerprint sensing surface 108(a) included for sensing andrecording the full fingerprint. The motion sensors are configured toseparately sense and recording motion information. Here, the sensorsurface 107(a) includes a motion sensor 110(a) configured separatelyfrom fingerprint sensing surface 108(a). According to this embodiment,the motion sensor is separate from the fingerprint sensing surface,though located on the same sensor surface. In operation, a fingerprintsurface 106 can be moved simultaneously along motion sensor 110(a) andfingerprint sensing surface 108(a). The motion information from themotion sensor, such as distance and time traveled over that distance,can be utilized together with the fingerprint sensing surface as an aidin reconstructing the separate portions of the fingerprint. As describedfurther below, such a single motion sensor can also be used fornavigation functions as well.

Referring to FIG. 4, another embodiment 102(b) of the invention isillustrated where motion sensors 110(b), 112(b) are located aboutfingerprint sensor surface 108(b) within sensor surface 107(b). Themotion sensor 110(b) is located along an anticipated axis of motion offinger 106 with respect to device 100 in directions A, B. Motion sensor110(b) can sense the distance and time expended over that distance todetermine velocity, which can be used in reconstructing the fingerprintportions simultaneously captured by fingerprint sensor surface 108(b).Using the additional motion sensors 112(b), a fingerprint surface 106can be sensed and captured even if a user slides the finger at an angleto the axis of the motion sensor 110(b). In fact, given the angles ofthe additional sensors 112(b) with respect to the central axis of thedevice, the direction of motion can be computed by a processor usingvector addition. Thus, the direction, distance and time expended duringfingerprint surface travel across the sensors can be used along with thefingerprint portions captured by the fingerprint sensor to accuratelyreconstruct the fingerprint image. This can be done with a fraction ofthe processing power, and thus less power source power, thanconventional methods and devices known in the prior art. Thus, theinvention provides great utility for fingerprint reconstruction andverification for devices that have power and processing restrictions. Asdescribed further below, such multiple motion sensors can also be usedfor navigation functions as well.

Referring to FIG. 5 a, yet another embodiment 102(C) of the invention isillustrated, where the motion sensors 110(C), 112(C) are interleavedwith fingerprint sensor surface 108(C) in a combined component withinsensor surface 107(C). Such a configuration can be created in a sensorsurface, where the pixels or data contact points that sense thefingerprint features are separately read from the sensors by aprocessor. For example, in a matrix of sensor pixels or data contactpoints, individual points can be singled out in one or more arrays tooperate as motion sensing arrays. In the same matrix, the remainingpixels or data contact points can form a fingerprint sensor surface forsensing and capturing the fingerprint image. In operation, a fingerprintcan be juxtaposed and moved along the sensor surface 107(C) along theanticipated axis of motion or at another angle, and an accurate senseand capture of a fingerprint can be achieved without undue computationand power load. While the fingerprint sensor surface 108(C) senses andcaptures the portions of images of the fingerprint features upon contactwith the fingerprint surface 106, the motion sensors can simultaneouslycapture motion information as the features move past the motion sensors.The motion information can be used in combination with the portions offingerprint images to reconstruct the fingerprint image. Referring toFIG. 5 b, the same configuration of FIG. 5 a is illustrated, with a viewof the motion sensors shown much smaller in comparison to the overallsensor surface. In a sensor surface that is densely populated withpixels or data contact points, the relative size of the portion of thesensor surface that is covered with the motion sensing arrays are verysmall compared to the pixels and data points that make up thefingerprint sensing surface 108(C), both located within sensor surface107(C). Thus, the fingerprint can be sensed and captured without anyinterference by the interleaved motion sensing arrays and accurateportions of a fingerprint image can be captured and accuratelyreconstructed using the combined information from the fingerprintsensors and the motion sensors. Utilizing this embodiment, a universalcomponent can be constructed and utilized for both motion detection andfingerprint capture, and the results from both functions can be utilizedto produce an efficient and power thrifty method of sensing,reconstructing and verifying a fingerprint. These motion sensors, whichcan sense both motion and direction, can also be used for navigationoperations.

Referring to FIG. 6, another embodiment 102(d) of the invention isillustrated, where a single motion sensor array 110(d) is interleavedwithin the fingerprint sensor surface 108(d) of sensor surface 107(d).Unlike the embodiment illustrated in FIGS. 5 a, 5 b, this embodiment islimited to one motion sensor array located along the anticipated axis ofmotion of the finger, which is anticipated to move in directions A, Bwith respect to the device 100. In operation, the interleaved sensorarray 110(d) can sense and capture motion information regarding themotion of the finger across the sensor surface 107(d), whilesimultaneously fingerprint sensor surface 108(d) can sense and capturethe fingerprint images for subsequent reconstruction. The informationfrom both sensors can be used to more accurately reconstruct thefingerprint image. The information of both motion and direction can alsobe used for navigation operations.

Referring to FIG. 7, yet another embodiment 102(e) of the invention isillustrated, where multiple motion sensors 112(e) are interleaved withinfingerprint sensor surface 108(e). This embodiment is similar to thatillustrated in FIGS. 5 a, 5 b, but with more motion sensors at variousangles. In operation, a fingerprint can be juxtaposed and moved alongthe sensor surface 107(e) along the anticipated axis of motion or atanother angle, and an accurate sense and capture of a fingerprint can beachieved without undue computation and power load. While the fingerprintsensor surface 108(e) senses and captures the portions of images of thefingerprint features upon contact with the fingerprint surface 106, themotion sensors can simultaneously capture motion information as thefeatures move past the motion sensors. The motion information can beused in combination with the portions of fingerprint images toreconstruct the fingerprint image. Those skilled in the art willunderstand that many variations on the concept of multiple motionsensors embedded or interleaved within the sensor surface are possible,and that different applications will have varying demands for thedifferent sensor features. The information of both motion and directioncan also be used for navigation operations.

If used for navigation purposes, of the motion sensor configurationsabove can be utilized for different navigation operations. For example,referring again to FIG. 3, the motion sensor 110(a) can be utilized onits own to sense motion in one axis of motion, for example in onedirection. One application may be a sensor used for a power, volume orother audio control, where an up or down motion can be used to adjustthe power, volume or other audio value. Another application for theinvention is the implementation of a scroll function for lists of dataor text in a GUI. Precise power control over a range may be useful inmanufacturing environments, where small changes in power can greatlyaffect a process. Another application may be to operate a medicalinstrument where accuracy is useful to the device's operation.

Navigation can be most useful in two dimensional space, where motion anddirection information are required. In prior art motion sensors, onlyone-directional motion can be detected, and, as discussed above, eventhe most basic motion detection requires a large amount of computationand processing resources. According to the invention, a navigationsensor can be configured to sense motion and direction. The motion anddirection information can then be processed for use in variousnavigation operations for devices, such as to operate as a computermouse for example. Referring again to FIG. 4, a separate motion sensor110(b) is illustrated for individual sensing of motion and direction,where distance, time expended over the distance (allowing forcalculation of velocity), and direction can be calculated. Though thismotion information can be used to enable better processing andreconstruction of fingerprint images as discussed above, it can be usedseparately for navigation, making it a navigation sensor. In operation,the separate motion sensor can detect motion and direction, givinginformation required for navigation functions. In operation, anavigation sensor can consistently computing the matches for the variousaxes, generating motion and direction information as a fingerprint movesabout a sensor.

Thus, if a user would stroke a fingerprint surface against a motionsensor surface, the arrays could pick up the motion and directioninformation, and a processor could process the information to generaterelative motion and direction information for use in navigation, such asfor a computer mouse. In this example, a user can move a finger relativeto a cursor on a graphical user interface (GUI), such as a computerscreen, a cellular phone, a personal data assistant (PDA) or otherpersonal device. The navigation sensor could then cause the cursor tomove relative to the fingerprint motion, and a user can navigate acrossthe GUI to operate functions on a computer or other device. Since themotion of the cursor is relative to the movement of the fingerprintsurface against the navigation sensor, relatively small movements cantranslate to equal, lesser or even greater distance movement of thecursor.

One aspect of the invention that is very useful to navigationconfigurations is the ability to consistently generate a motion result.As discussed above, the invention provides a means to substantiallyensure a result when a fingerprint moves across a motion sensor. This istrue for single array motion sensors as well as multiple array sensorsused for two-dimensional motion processing. In a navigation application,such a configuration can provide accurate and consistent motion anddirectional information that allows for smooth and reliable navigationaloperations.

Referring to FIG. 8A, another embodiment of the invention isillustrated, where multiple arrays are located on the sensor surface toallow for sensing and capturing motion and direction information indifferent directions of fingerprint travel for use in navigationapplications and other applications. The base film 120, which may be a35 mm film or other material, includes a sensor surface 121 havingseveral motion sensor arrays. Similar to the three sensor arrayillustrated in FIG. 5A, there are three sensors that fan upward fordetecting motion and direction. In operation, a user typically willstroke over the sensor in a downward direction, and the three sensorscan determine the direction and speed using vector analysis. However, itmay be desired to account for motion in either an upward or downwarddirection, and multiple sensors in either direction would be useful tobetter capture the information. From an orientation of a user facing thesensor illustrated in FIG. 8( a), the right sensors 122,124 face theright, and are configured to capture movement toward the right, whereeither sensor could capture movement motion from the upper right to thelower left, and from the upper left to the lower right. Sensors 126,128could capture up or down movement, and sensors 130,132 face the left,and are configured to capture movement toward the right, where eithersensor could capture movement motion from the upper right to the lowerleft. Utilizing the multiple sensors, a sensor would be more robust,capable of sensing more fingerprint features, and also able to processmore movement and directional information for use in capturing andreconstructing fingerprint images or for other applications such asnavigation. The angle θ occurring between sensor 121 and centerhorizontal line 134 can be any angle, such as 30, 45 or 22.5 degrees inorder to most effectively capture movement that is not aligned withcenter sensors 126,128. All off-axis sensors 124,128,130,132 can be setat various angles, which can depend on a particular application.

Referring to FIG. 8B, an even more robust example of a sensor set onfilm 136 having a surface 137 located on the film. The sensor 138 islocated on the film surface 137, and includes multiple array sensors 140that are set at various angles. In this embodiment, each array may beset at 22.5 degrees from adjacent angles, providing a wide variety ofangles at which to sense and capture motion information. The sensor,similar to that of FIGS. 8( a) and 2B, has an IC chip 139 that isseparate from the sensor surface 138.

Referring to FIG. 8C, a diagrammatic view of multiple array sensorslocated on a sensor 142 is illustrated. Sensors 144,144′ are verticalarrays that are set to capture one axis of motion. Sensors 146,146′ and150,150′ are located off axis at an angle to sensors 144,144′. Sensors148,148′ are optional and may be used in conjunction with the othersensors to gather motion information in a horizontal direction withrespect to the vertical sensors. In practice, either or all of thesesensors can be utilized by a system to accurately sense and capturemotion and direction information in multiple directions. Again, whichsensors to use may depend on a particular application and configuration.

In one embodiment, in order to support motion at any arbitrary angle,sensor arrays may be oriented at approximately 0, 30, 60, 90, 120, and150 degrees. Another more robust system might space them at 22.5 degreeincrements, rather than 30. Once motion reaches 180 degrees, the processcan use reverse motion on the zero degree sensor array, and so on. Adevice configured in this way would have some of the properties of anavigation touchpad such as those used in laptop computers, with therelative motion sensing capability of a computer mouse.

Referring to FIG. 9A, a diagrammatic view of a sensing device 100configured according to the invention is illustrated. The deviceincludes a linear array 112 such as described in the embodiments above,and also includes a sensor element 102 also discussed above. The devicefurther includes sensor control logic 252 configured to control thebasic operations of the sensor element. The exact operations of thesensor element governed by the sensor logic control greatly depends on aparticular sensor configuration employed, which may include such aspower control, reset control of the pixels or data contact points,output signal control, cooling control in the case of some opticalsensors, and other basic controls of a sensor element. Sensor controlsare well known by those skilled in the art, and, again, depend on theparticular operation. The device further includes a readout circuit 254for reading analog output signals from the sensor element when it issubject to a fingerprint juxtaposed on the sensor surface 107. Thereadout circuit includes an amplifier 256 configured to amplify theanalog signal so that the it can more accurately be read in subsequentoperations. Low pass filter 258 is configured to filter out any noisefrom the analog signal so that the analog signal can be more efficientlyprocessed. The readout circuit further includes an analog to digitalconverter 260 that is configured to convert the output signal from thesensor element to a digital signal that indicates a series of logic 0'sand 1's that define the sensing of the fingerprint features by thepixels or data contact points of the sensor surface 107. Such signalsmay be separately received by the motion sensors and the fingerprintsensing surfaces as discussed in the embodiments above, and may be readout and processed separately. The readout circuit may store the outputsignal in storage 262, where fingerprint data 264 is stored andpreserved, either temporarily until the processor 266 can process thesignal, or for later use by the processor. The processor 216 includesarithmetic unit 268 configured to process algorithms used for navigationof a cursor, such as that described in connection with navigationfeatures of FIG. 2 b, and for reconstruction of fingerprints. Processinglogic 270 is configured to process information and includes analog todigital converters, amplifiers, signal filters, logic gates (all notshown) and other logic utilized by a processor. Persistent memory 274 isused to store algorithms 276 and software applications 278 that are usedby the processor for the various functions described above, and in moredetail below. The system bus 280 is a data bus configured to enablecommunication among the various components in the system 100.

Referring to FIG. 9B, another embodiment of the invention is illustratedas a system 100 configured to sense, capture and process navigationinformation. The device includes a linear navigation array(s) 112 suchas described in the embodiments above, and also includes a sensorelement 102 also discussed above. The surface may include a single arrayfor one-dimensional navigation capabilities, or may include multiplearrays for capturing both motion and directional information for use innavigation applications. The device further includes sensor controllogic 252 configured to control the basic operations of the sensorelement. The exact operations of the sensor element governed by thesensor logic control greatly depends on a particular sensorconfiguration employed, which may include such as power control, resetcontrol of the pixels or data contact points, output signal control,cooling control in the case of some optical sensors, and other basiccontrols of a sensor element. Sensor controls are well known by thoseskilled in the art, and, again, depend on the particular operation. Thedevice further includes a readout circuit 254 for reading analog outputsignals from the sensor element when it is subject to a fingerprintjuxtaposed on the sensor surface 107. The readout circuit includes anamplifier 256 configured to amplify the analog signal so that the it canmore accurately be read in subsequent operations. Low pass filter 258 isconfigured to filter out any noise from the analog signal so that theanalog signal can be more efficiently processed. The readout circuitfurther includes an analog to digital converter 260 that is configuredto convert the output signal from the sensor element to a digital signalthat indicates a series of logic 0's and 1's that define the sensing ofthe fingerprint features by the pixels or data contact points of thesensor surface 107. Such signals may be separately received by themotion sensors and the fingerprint sensing surfaces as discussed in theembodiments above, and may be read out and processed separately. Thereadout circuit may store the output signal in storage 262, wherefingerprint data 264 is stored and preserved. Navigation data 282 mayalso be stored in storage 262 for use according to the invention. Thismay be stored either temporarily until the processor 266 can process thesignal, or for later use by the processor. The processor 216 includesarithmetic unit 268 configured to process algorithms used for navigationof a cursor, such as that described in connection with navigationfeatures of FIG. 2 b, and for reconstruction of fingerprints. Processinglogic 270 is configured to process information and includes analog todigital converters, amplifiers, signal filters, logic gates (all notshown) and other logic utilized by a processor. Persistent memory 274 isused to store algorithms 276, software applications 278 and navigationsoftware application 279 that are used by the processor for the variousfunctions described herein. The system bus 280 is a data bus configuredto enable communication among the various components in the system 100.

FIG. 10 depicts the operation of the invention as a section 101 offingerprint 100 passes over the sensor array 202. Sensor array 202 iscomprised of a number of imaging pixel elements arranged along the axisof motion of the finger with a sufficient pixel density to resolvefingerprint ridges and valleys, typically 250-500 dpi. The pixels maysense the presence or absence of the fingerprint ridge through a varietyof techniques, such as capacitance, optical imaging, or mechanicalpressure. The array of imaging pixels 202 is sampled at a predeterminedrate, sufficient to ensure that the finger will not travel more than twopixels in a sample period. Any reasonable time period could be set, butone example is 500 usec. In this embodiment, the pixels are configuredas a single extended array, and software may subdivide the larger arrayinto a number of potentially overlapping windows.

At each sample time, the state of the sense elements is converted to aseries of numerical values from digitized segments 203 a, 203 b. For thesake of simplification, digitized segments 203 a,203 b shows a binarydigitization, indicating presence or absence of ridge. The sensor valuesmay be encoded with a higher precision if the chosen sensor methodologyallows. Because the two image samples 203 a and 203 b were taken alongthe axis of motion 106 at different times, they may be sequentiallyshifted and compared against each other until a match is found for anabsolute distance of motion D in the period between the samples T,resulting in a direct finger velocity measurement D/T.

Unlike conventional systems and methods, the system does not have toaccumulate a large time history when no motion is detected betweensamples 203 a and 203 b. It can simply maintain the earlier sample 203a, and perform a new computation when the next sample is acquired. Thisis advantageous in the case where there is no prior knowledge of theapproximate velocity speed of the finger. Often in practice, the fingervelocity relative to the sensory surface may vary greatly. The inventioneliminates the need for a large buffer of samples to cover a widedynamic range of finger speeds.

A further advantage offered by the invention is the ability to adjustthe sample rate and therefore the distance of motion traveled betweensamples as a function of finger velocity. As the finger velocityincreases, the number of sample periods required to traverse between twoadjacent pixels decreases. This effectively decreases the resolution ofa velocity measurement. And, as the uncertainty of the measurementapproaches the measurement period, all resolution is lost. Accordingly,in order to maintain the accuracy of the estimated velocity, themeasurement system may adjust the sample rate to optimize the distancetraveled when looking for a match between two frames. For example,requiring ten pixels of motion at fast finger swipe speeds can ensure a10% accuracy in velocity measurements. Conversely, as the fingervelocity decreases, the number of time samples required to travel asignificant distance increases. In this case, the system could decreasethe sample rate and reduce the distance traveled for a match to aslittle as one pixel. This would provide a significantly more rapidresponse to motion changes in navigation applications and would bettertract finger velocity changes used to reconstruct two dimensional imagesfrom a one dimensional sensor. Those skilled in the art will understandthat there are various methods for changing the sample rate in order toachieve these and other objectives, and the invention is not limited toany particular method, and moreover is inclusive of the various knownmethods as well as methods readily ascertainable by one skilled in theart without undue experimentation.

FIGS. 11 a and 11 b show the digitization results sampled at twoinstances 203 a and 203 b as the finger moves in a downward direction306. In this example, the finger has traveled downward approximately 7pixels between samples 303 a and 303 b. FIGS. 11 a-11 j illustrateresults from a similarity comparison between samples 203 a and 203 bthat were converted into binary numbers, giving the following matchresults:

Pixel Shift FIG. 12 Score 0 (a) (9/16)~.56 1 (b) (7/15)~.47 2 (c)(9/14)~.64 3 (d) (4/13)~.31 4 (e) (7/12)~.58 5 (f) (8/11)~.73 6 (g)(1/10) = .10 7 (h) (8/9)~.89 8 (j) (3/8)~.38The match results show a strong correlation with the actual motion ofseven pixels of vertical distance clearly distinguished in just onesample pair, even though the ridge frequency is fairly uniform for theselected segment of the fingerprint. It should also be clear to thoseknowledgeable in the art that the accuracy of the match would besignificantly enhanced by additional levels of gray scale in the pixeldata.

FIGS. 12 a and 12 b depict an embodiment of the invention that includesthree linear arrays disposed at different angles to measure motionacross a range of angles from the principal axis (in this case+/−25degrees from the main axis). The central imaging array 301 is augmentedwith an array 302 oriented at a −25 degree angle to the central axis andan array 303 oriented at a +25 degree angle to the central axis. It willbe understood by those skilled in the art that, given this disclosure,various different angles of the arrays can be implemented, as well asdifferent numbers of arrays. In FIG. 12 a we see the image of afingerprint at the initial starting position superimposed on the sensorarrays, and the resulting binary images 304 a,305 a, and 306 a with thefinger in the initial position. In FIG. 12 b, the finger has moved ashort distance at an approximately +25 degree angle shown betweenpositions 310 and 311, and the resulting binary images are shown in 304b,305 b, and 306 b. The following table shows the results of binarycomparison for the pairings of 304 a/304 b,305 a/305 b, and 306 a/306 busing the shift and compare method previously described:

Pixel Score Shift Score 304 305 Score 306 0 0.38 0.44 0.38 1 0.67 0.470.67 2 0.64 0.43 0.21 3 0.38 0.54 0.77 4 0.50 0.33 0.50 5 0.82 0.36 0.186 0.40 0.60 1.00 7 0.44 0.44 0.22 8 0.50 0.25 0.50

Because the motion principally follows the axis of sensor 303, thecorrelation for the pairing 306 a/306 b is strong at the correct sixpixel distance, but the pairings 304 a/304 b, and 305 a/305 b show weakcorrelation. When the direction of motion is at an angle between theaxes of any two of the sensor arrays, a correlation will be found inboth of the sensors, and the true motion will be found by taking thevector sum of the estimates from the two sensors.

The example above covers the simple case where the motion is completelyaligned with one of the sensor axes. In the case of motion that liesbetween two axes, the distance a feature travels along a sensor arraywill be less than the entire length of the sensor. To detect motionacross a range of angles, sensor arrays must be provided at a series ofangles disposed so that a match will be found on at least two of thesensor arrays. For example, by arranging the arrays in 30 degreeincrements across the allowable range of motion axes, it is possible toensure that if there is worst case alignment (i.e. a 15 degreemisalignment between the actual axis of motion an the two sensor arrayson either side of it), an image feature will still approximately followthe nearest sensor arrays for more than three pixels of travel. Thus, bysampling the sensor arrays fast enough to ensure that the finger has nottraveled more than three pixels between samples, it is possible todetermine the axis of motion by finding the adjacent pair of sensorswith the highest correlation, and computing the vector sum of thedistances traveled along each of them.

Referring to FIG. 12( c), a flow chart 1200 is illustrated that showsone embodiment of a motion sensor process that can be used for simplydetecting and sensing motion, in conjunction with an image sensor foruse in reconstructing a fingerprint image, for use in navigationapplications or other applications where accurate motion sensing isdesired. The process begins at step 1202. In step 1204, an initialsample array of a fingerprint is sensed. In step 1204, a second samplearray is sensed after a period of time, t=n. The arrays are convertedinto a digital representation of the array of fingerprint sensors, and adigital string of digital ones and zeros is used by a processor todetermine the relative movement between the two samplings. In practice,a predetermined period of time can be selected, or it can alternativelybe measured, where time is measured between the first and secondsamples. In either case, once the distance is determined between the twosamples, assuming that movement has occurred, velocity can be calculatedusing the distance traveled divided by the time expended during suchtravel. Continuing, in step 1208, the two arrays are compared. In aninitial alignment, referring briefly to FIG. 10, the arrays are comparedside by side. If this comparison shows a high correlation, then it isindicative of no relative motion between the fingerprint and the motionsensor.

In step 1210, a similarity score is generated, defining the amount ofcorrelation between the two arrays. This may be in the form of aprobability value, a percentage correlation value, or other mathematicalvalue that can be used by the processor to determine the best similarityscore among different comparisons. In step 1212, it is determine whetherthe similarity score falls within a threshold. In one embodiment, thethreshold is a predetermined number that is decided according to aparticular application. In practice, the invention can be configured toproduce correlations that are of a high value, thus justifying a highthreshold. Those skilled in the art will understand that such athreshold can be determined without undue experimentation, and that isdepends on an application. If the score does not fall within thethreshold, then the arrays are shifted to offset alignment in step 1214.The direction of the shifting may be done according to a predicteddirection that a user would be expected to move the fingerprint surfaceacross the sensor. If it is not known, or if the design calls for eitherdirection, then flexibility can be accommodated by shifting the arraysin multiple directions until an alignment is reached that is within thethreshold. In either case, the process returns to step 1208, where thearrays are compared again. A new similarity score is generated in step1210, and the new score is measured against the threshold. This processcan be reiterated until a score passes the threshold, and could possiblyregister an error if one is not met over time or a predetermined numberof cycles. In a practical application, the two arrays can be shifted andprocessed once for each pixel in one array, since they are equal inlength given that they were taken from the same array. If a score occursthat is within the threshold, then the distance is estimated in step1216. This can be done by simply counting the number of pixels in whichthe arrays were shifted before a score occurs within the threshold, andmultiplying this number by the distance between pixels, which can beestimated to be the distance between midpoints of two pixels. Thedistance can be accurately measured by sampling distances betweenindividual pixels and groups of pixels in an array, but the exact methodof measurement would depend on the application. Then, the velocity canbe estimated in step 1218 by dividing the distance traveled by the timeexpended during the travel. The process ends at step 1220, where anestimated velocity value can be generated.

Referring to FIG. 13, another flow chart 1300 is illustrated that showsone embodiment of a motion sensor process that can be used for simplydetecting and sensing motion, in conjunction with an image sensor foruse in reconstructing a fingerprint image, for use in navigationapplications or other applications where accurate motion sensing isdesired. The process begins at step 1302. In step 1304, an initialsample array of a fingerprint is sensed. In step 1304, a second samplearray is sensed after a period of time, t=n. The arrays are convertedinto a digital representation of the array of fingerprint sensors, and adigital string of digital ones and zeros is used by a processor todetermine the relative movement between the two samplings. In practice,a predetermined period of time can be selected, or it can alternativelybe measured, where time is measured between the first and secondsamples. In either case, once the distance is determined between the twosamples, assuming that movement has occurred, velocity can be calculatedusing the distance traveled divided by the time expended during suchtravel.

Continuing, in step 1308, the two arrays are compared. In an initialalignment, referring briefly to FIG. 10, the arrays are compared side byside. If this comparison shows a high correlation, then it is indicativeof no relative motion between the fingerprint and the motion sensor. Instep 1310, a similarity score is generated, defining the amount ofcorrelation between the two arrays. This may be in the form of aprobability value, a percentage correlation value, or other mathematicalvalue that can be used by the processor to determine the best similarityscore among different comparisons. In step 1312, it is determine whetherthe shift is a last shift in a predetermined number of shifts. Inpractice, it is practical to shift at least the number of pixels in thearray sensor, since both image arrays are sensed and sampled by the samesensor array. Again, similar to the process invention embodied in FIG.12, the direction of the shifting may be done according to a predicteddirection that a user would be expected to move the fingerprint surfaceacross the sensor. If it is not known, or if the design calls for eitherdirection, then flexibility can be accommodated by shifting the arraysin multiple directions until an alignment is reached that is within thethreshold. If it is not the last shift, then the array is shifted instep 1314, and the process returns to step 1308, where the arrays areagain compared, a new score is generated in step 1310, and it is againqueried whether it is the last shift. If it is the last shift, then thehighest similarity score is chosen in step 1316.

Then the distance is estimated in step 1318. Again, this can be done bysimply counting the number of pixels in which the arrays were shifted,and multiplying this number by the distance between pixels, which can beestimated to be the distance between midpoints of two pixels. Thedistance can be accurately measured by sampling distances betweenindividual pixels and groups of pixels in an array, but the exact methodof measurement would depend on the application. Then, the velocity canbe estimated in step 1320 by dividing the distance traveled by the timeexpended during the travel. The process ends in step 1322 where avelocity value can be generated.

Referring to FIG. 14, a flow chart of another embodiment of a navigationsensor operation is illustrated, where multiple sensors are used toproduce navigation information from a navigation sensor. The processbegins Referring to FIG. 14, another flow chart 1400 is illustrated thatshows one embodiment of a motion sensor process that can be used forsimply detecting and sensing motion, in conjunction with an image sensorfor use in reconstructing a fingerprint image, for use in navigationapplications or other applications where accurate motion sensing isdesired. The process begins at step 1402. In step 1404, initial samplearrays of a fingerprint are sensed. In step 1404, a second set of samplearrays are sensed after a period of time, t=n. The arrays are convertedinto a digital representation of the array of fingerprint sensors, and adigital string of digital ones and zeros is used by a processor todetermine the relative movement between the each of the two samplingsfrom each sensor. In practice, a predetermined period of time can beselected, or it can alternatively be measured, where time is measuredbetween the first and second samples. In either case, once the distanceis determined between the two samples, assuming that movement hasoccurred, velocity can be calculated using the distance traveled dividedby the time expended during such travel, and direction can be determinedusing vector analysis of the several vectors' motion information.

Continuing, in step 1408, the two arrays are compared for each sensor.In an initial alignment, referring briefly to FIG. 10, the digitalrepresentation of the arrays of features are compared side by side foreach sensor array. If this initial comparison shows a high correlation,then it is indicative of no relative motion between the fingerprint andthe motion sensor. In step 1410, a similarity score is generated foreach array, defining the amount of correlation between the two arrays.This may be in the form of a probability value, a percentage correlationvalue, or other mathematical value that can be used by the processor todetermine the best similarity score among different comparisons. In step1412, it is determine whether the shift is a last shift in apredetermined number of shifts. In practice, it is practical to shift atleast the number of pixels in each of the array sensors, since bothimage arrays from each sensor is sensed and sampled by the same sensorarray. Again, similar to the process invention embodied in FIG. 12, thedirection of the shifting may be done according to a predicted directionthat a user would be expected to move the fingerprint surface across thesensor. If it is not known, or if the design calls for either direction,then flexibility can be accommodated by shifting the arrays in multipledirections until an alignment is reached that is within the threshold.If it is not the last shift, then the array is shifted in step 1414, andthe process returns to step 1408, where the arrays are again compared, anew score is generated in step 1410, and it is again queried whether itis the last shift. If it is the last shift, then the highest similarityscore is chosen in step 1416. In step 1417, the predominant direction ofmotion is determined by selecting the array with the highest similarityscore at its local maximum. The arrays adjacent to the array at thepredominant motion axis are examined to determine if either theirsimilarity scores exceeds the threshold for a secondary component axis(this threshold is lower than the threshold for the predominant axis).

Then the distance is estimated in step 1418. Again, this can be done bysimply counting the number of pixels in which the arrays were shifted,and multiplying this number by the distance between pixels, which can beestimated to be the distance between midpoints of two pixels. Thedistance can be accurately measured by sampling distances betweenindividual pixels and groups of pixels in an array, but the exact methodof measurement would depend on the application.

If the similarity score for either of the adjacent arrays exceeds thethreshold and this similarity score occurs at a distance less than thedistance traveled on the predominant axis, then the principal axis ofmotion is assumed to lie between the predominant axis and this secondaxis. The angle of motion is then estimated by computing the ratio ofdistances along the predominant and secondary axes. The ratio of thesedistances is approximately equal to the ratio of the cosines of theangles between the actual axis of motion and the axes of the two sensorarrays.

The final estimated distance is computed by taking the distance measuredon the predominant axis sensor and dividing it by the cosine of thedifference between the estimated angle of motion and the angle of thesensor axis.

Then, the velocity can be estimated in step 1420 by dividing thedistance traveled by the time expended during the travel. The processends in step 1422 where a velocity value can be generated.

Referring to FIG. 15, a flow chart 1500 of one embodiment of anavigation sensor operation is illustrated. The process begins at step1502, and, in step 1504, motion information is received, such asdistance, time and velocity information. In step 1506, directioninformation is received from the sensors. In step 1508, relative motionfor navigation is calculated by a processor. In step 1510, directioninformation for navigation is calculated. And, in step 1512, navigationoperations are performed. The process ends at step 1514.

Referring to FIG. 16, a flow chart of one embodiment of a navigationsensor operation, specifically the operation of a cursor on a monitor,is illustrated. The process begins in step 1602, and in 1604 fingermotion information is received, such as distance, time and velocity. Instep 1606, finger direction information is received. In step 1608,relative motion and direction factors are calculated for use inoperating the cursor. In step 1610, the cursor is moved according to therelative motion and direction factors calculated in step 1610. Theprocess ends in step 1612.

The invention may also involve a number of functions to be performed bya computer processor, such as a microprocessor. The microprocessor maybe a specialized or dedicated microprocessor that is configured toperform particular tasks by executing machine-readable software codethat defines the particular tasks. The microprocessor may also beconfigured to operate and communicate with other devices such as directmemory access modules, memory storage devices, Internet relatedhardware, and other devices that relate to the transmission of data inaccordance with the invention. The software code may be configured usingsoftware formats such as Java, C++, XML (Extensible Mark-up Language)and other languages that may be used to define functions that relate tooperations of devices required to carry out the functional operationsrelated to the invention. The code may be written in different forms andstyles, many of which are known to those skilled in the art. Differentcode formats, code configurations, styles and forms of software programsand other means of configuring code to define the operations of amicroprocessor in accordance with the invention will not depart from thespirit and scope of the invention.

Within the different types of computers, such as computer servers, thatutilize the invention, there exist different types of memory devices forstoring and retrieving information while performing functions accordingto the invention. Cache memory devices are often included in suchcomputers for use by the central processing unit as a convenient storagelocation for information that is frequently stored and retrieved.Similarly, a persistent memory is also frequently used with suchcomputers for maintaining information that is frequently retrieved by acentral processing unit, but that is not often altered within thepersistent memory, unlike the cache memory. Main memory is also usuallyincluded for storing and retrieving larger amounts of information suchas data and software applications configured to perform functionsaccording to the invention when executed by the central processing unit.These memory devices may be configured as random access memory (RAM),static random access memory (SRAM), dynamic random access memory (DRAM),flash memory, and other memory storage devices that may be accessed by acentral processing unit to store and retrieve information. The inventionis not limited to any particular type of memory device, or any commonlyused protocol for storing and retrieving information to and from thesememory devices respectively.

The apparatus and method include a method and apparatus for enabling andcontrolling fingerprint sensors and fingerprint image data and motiondata in conjunction with the operation of a electronic device wherenavigation and fingerprint verification processes are utilized. Althoughthis embodiment is described and illustrated in the context of devices,systems and related methods of imaging fingerprints and navigationfeatures for a portable device, the scope of the invention extends toother applications where such functions are useful. Furthermore, whilethe foregoing description has been with reference to particularembodiments of the invention, it will be appreciated that these are onlyillustrative of the invention and that changes may be made to thoseembodiments without departing from the principles of the invention.

1. A fingerprint motion tracking apparatus for use in navigationapplications, comprising: a linear sensor array configured to sensefeatures of a fingerprint along an axis of finger motion, the linearsensor array including a plurality of substantially contiguous sensingelements configured to capture segments of image data; a bufferconfigured to receive and store image data from the linear sensor array;and a processing element configured to generate fingerprint motion datafor use in navigation.
 2. An apparatus according to claim 1, wherein thelinear sensor array is configured to repeatedly sense at least twooverlapping line segments of fingerprint data, and wherein the processoris configured to generate motion data based on at least two sensedoverlapped line segments of fingerprint data and navigation data basedon relative motion of a fingerprint relative to an object beingnavigated.
 3. An apparatus according to claim 2, wherein the objectbeing navigated is a cursor on a graphical user interface.
 4. Anapparatus according to claim 1, wherein the motion data includesvelocity and directional data.
 5. A fingerprint motion trackingapparatus according to claim 1, wherein the linear sensor array isconfigured to sense a first set of features of a fingerprint along anaxis of finger motion and to generate a first set of image data capturedby a plurality of substantially contiguous pixels of the sensor arrayand is also configured to subsequently sense a second set of features ofthe fingerprint along an axis of finger motion and to generate a secondset of image data captured by a plurality of substantially contiguouspixels of the sensor array, and wherein the processing element isconfigured to compare first and second sets of image data to determinethe distance traveled by the fingerprint over a time interval, andwherein the distance and time interval are used to calculatenavigational data for navigating a cursor on a graphical user interfacerelative to the motion of a fingerprint across the sensor.
 6. Afingerprint motion tracking apparatus according to claim 1, furthercomprising another linear sensor array configured to sense features of afingerprint and to generate directional image data captured by aplurality of substantially contiguous pixels, wherein the processingelement is configured to produce navigation data using the motion datato assemble contiguous image portions aligned along a second line ofmotion.
 7. A fingerprint motion tracking apparatus according to claim 1,further comprising another linear sensor array aligned along anotheraxis of finger motion and configured to sense features of a fingerprintand to generate directional image data captured by a plurality ofsubstantially contiguous pixels for use in navigation operations of anobject relative to the motion of a fingerprint across the linearsensors.
 8. A fingerprint motion tracking apparatus according to claim1, further comprising a plurality of linear sensor arrays configured tosense features of a fingerprint and to generate directional image datacaptured by a plurality of substantially contiguous pixels, wherein theprocessing element is configured to produce navigation data using themotion data to assemble contiguous image portions.
 9. A method oftracking motion of a fingerprint with respect to a sensor for use innavigation operations, comprising: sensing at least two consecutiveoverlapping line segments of a fingerprint image features located alongan axis of motion of the fingerprint surface with respect to the sensorsurface; storing digital data corresponding to the line segments of afingerprint image features sensed by the sensing elements; andprocessing the digital data to generate fingerprint motion data andnavigation data relative to an object being navigated.
 10. A methodaccording to claim 9, further comprising: comparing digital data of aseries of fingerprint image features with a subsequently sensed seriesof fingerprint image features; determining the amount of shift betweenthe series of fingerprint image features and the subsequently sensedseries of fingerprint image features to determine the distance traveledby the fingerprint across a sensor; and generating navigation data foruse in navigating an object relative to the fingerprint motion.
 11. Amethod according to claim 10, further comprising: estimating thedistance traveled by the fingerprint surface with respect to the sensorsurface by multiplying the pixel shift detected between subsequentimages times the physical distance of the image pixels in the sensor;and computing the velocity of the fingerprint surface with respect tothe sensor surface by dividing the estimated distance by the timeexpended between the sensing of the fingerprint image features and thesubsequently sensed fingerprint image features.
 12. A method accordingto claim 11, further comprising: estimating the distance traveled by thefingerprint surface with respect to the sensor surface by multiplyingthe multiplying the pixel shift detected between subsequent images timesthe physical distance between pixels in the sensor; and computing thevelocity of the fingerprint surface with respect to the sensor surfaceby dividing the estimated distance by the time expended between thesensing of the fingerprint image features and the subsequently sensedfingerprint image features.
 13. A method of tracking motion of afingerprint with respect to a sensor for use in navigation operations,comprising: collecting a time sequence of image samples from a linearsensory array, wherein each sample has a series of pixel valuescorresponding to substantially contiguous fingerprint image features;generating a list of similarity match scores by comparing each imagesample with a previous sample; determining the pixel shift of two imagesamples having the highest similarity match score; estimating thedistance traveled by multiplying the number of pixels in an image sampletimes the physical distance between pixels; computing a velocityestimate by dividing the estimated distance by the time expended betweencollecting the two samples with the highest match score navigating anobject relative to the velocity estimate.
 14. A method of trackingmotion of a fingerprint with respect to a sensor for use inelectronically navigating an object, comprising: collecting a timesequence of images values from each of a plurality of linear imagesensor arrays; generating separate lists of similarity match scores foreach linear image sensor array by comparing successively shiftedversions of each image sample with a previous sample; determining whichlinear sensor array produced the highest similarity match score torepresent the principal axis of motion; determining the pixel shift ofthe linear sensor array that has the highest similarity match score;estimating the distance traveled along the principal axis by multiplyingthe number of pixels times the physical distance between pixels;computing the velocity of the fingerprint surface with respect to thesensor surface; and computing the relative movement of a fingerprintwith respect to an object being navigated.
 15. A method according toclaim 14, further comprising: determining the sensor array adjacent tothe principal axis that had the next highest similarity score torepresent the secondary axis of motion; determining the pixel shift ofthe secondary axis with the highest similarity match score; and if thepixel shift of the pixels on the secondary axis is less than the pixelshift of the pixels on the primary axis, computing the final velocityand direction as the vector sum of the pixels on the secondary axis andthe pixels on the primary axis.
 16. A method according to claim 15,further comprising: generating navigation information for navigating anobject relative to fingerprint motion using the final velocity anddirection computed.
 17. A fingerprint motion tracking apparatus forproducing navigation information, comprising: a linear sensor arrayconfigured to sense features of a fingerprint along an axis of fingermotion, the linear sensor array including a plurality of substantiallycontiguous sensing elements configured to capture a plurality ofsegments of fingerprint image data; a buffer configured to receive andstore image data from the linear sensor array; and a processing elementconfigured to generate motion data for use in navigation operations. 18.A fingerprint motion tracking apparatus according to claim 17, furthercomprising at least one other linear sensor array configured to sensefeatures of a fingerprint and to generate directional image datacaptured by a plurality of substantially contiguous pixels, wherein theprocessing element is configured to produce navigation data using themotion data to assemble contiguous image portions.
 19. A fingerprintmotion tracking system for producing navigation information, comprising:means for sensing features of a fingerprint along an axis of fingermotion, the with a plurality of substantially contiguous sensingelements configured to capture a plurality of segments of fingerprintimage data; buffer means for receiving and storing image data from themeans for sensing features of a fingerprint; and processing means forgenerating navigation data.
 20. A system according to claim 19, furthercomprising means for producing navigation data using motion anddirection data to assemble contiguous image portions.
 21. A systemaccording to claim 19, further comprising means for generating separatelists of similarity match scores for each sensing element comparingsuccessively shifted versions image samples with a previous sample;means for determining which sensing element produced the highestsimilarity match score to represent a principal axis of motion; meansfor determining the pixel shift of the sensing element that has thehighest similarity match score; means for estimating the distancetraveled along the principal axis by multiplying the number of pixelstimes the physical distance between pixels; means for computing thevelocity of the fingerprint surface with respect to a sensing element;and means for computing the relative movement of a fingerprint withrespect to an object being navigated.
 22. A system according to claim21, further comprising: means for determining which sensor arrayadjacent to a principal axis that had the next highest similarity scoreto represent the secondary axis of motion; and means for determining thepixel shift of the secondary axis with the highest similarity matchscore; wherein, if the pixel shift of the pixels on the secondary axisis less than the pixel shift of the pixels on the primary axis,computing the final velocity and direction as the vector sum of thepixels on the secondary axis and the pixels on the primary axis.
 23. Asystem according to claim 22, further comprising: means for generatingnavigation information for navigating an object relative to fingerprintmotion using the final velocity and direction computed.